build-sys: meson: support elogind alternative for module-systemd-login

Part-of: <https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/502>

meson.build

@@ -655,6 +655,11 @@ if systemd_dep.found() and systemduserunitdir == ''
   systemduserunitdir = systemd_dep.get_pkgconfig_variable('systemduserunitdir')
 endif
 
+libelogind_dep = dependency('libelogind', required : get_option('elogind'))
+if libelogind_dep.found()
+  cdata.set('HAVE_SYSTEMD_LOGIN', 1)
+endif
+
 tcpwrap_dep = cc.find_library('wrap', required: get_option('tcpwrap'))
 if cc.has_header('tcpd.h') and cc.has_function('hosts_access', dependencies : tcpwrap_dep)
   cdata.set('HAVE_LIBWRAP', 1)
@@ -899,6 +904,7 @@ summary = [
   'Enable udev:                   @0@'.format(udev_dep.found()),
   '  Enable HAL->udev compat:     @0@'.format(get_option('hal-compat')),
   'Enable systemd:                @0@'.format(libsystemd_dep.found()),
+  'Enable elogind:                @0@'.format(libelogind_dep.found()),
   'Enable TCP Wrappers:           @0@'.format(tcpwrap_dep.found()),
   'Enable libsamplerate:          @0@'.format(samplerate_dep.found()),
   'Enable IPv6:                   @0@'.format(get_option('ipv6')),

meson_options.txt

@@ -93,6 +93,9 @@ option('bluez5-ofono-headset',
 option('dbus',
        type : 'feature', value : 'auto',
        description : 'Optional D-Bus support')
+option('elogind',
+       type : 'feature', value : 'auto',
+       description : 'Optional elogind support')
 option('fftw',
        type : 'feature', value : 'auto',
        description : 'Optional FFTW support')

src/modules/meson.build

@@ -203,9 +203,9 @@ if openssl_dep.found()
   endif
 endif
 
-if libsystemd_dep.found()
+if libsystemd_dep.found() or libelogind_dep.found()
   all_modules += [
-    [ 'module-systemd-login', 'module-systemd-login.c', [], [], [libsystemd_dep] ],
+    [ 'module-systemd-login', 'module-systemd-login.c', [], [], [libsystemd_dep, libelogind_dep] ],
   ]
 endif